Spinal Cord Localization

Question 1

what do LMN do and what 4 things are observed with LMN disease?

Answer 1

LMN cause contraction of flexor and extensor muscles; in disease will see
1. short and choppy gait
2. decreased reflexes
3. decreased muscle tone
4. muscle atrophy

Question 2

what do UMN do and what 4 things are observed in UMN disease?

Answer 2

UMN tell LMN what to do to maintain posture and generate gait; in disease will see:
1. long and lopey gait
2. normal to increased reflexes
3. normal to increased muscle tone
4. normal muscle size

Question 3

describe mentation and cranial nerves with spinal cord lesions

Answer 3

mentation and cranial nerves both usually normal

Question 4

at what point can you draw a line in the spinal cord and place a UMN lesion cranial to the line that will affect all 4 limbs?

Answer 4

draw a line between T2-T3, because the C6-T2 spinal cord segments give rise to the nerves of the thoracic limb; since UMN descend to facilitate and inhibit LMN in both thoracic and pelvic limbs, a lesion cranial to T2 will affect all 4 limbs

Question 5

what will a lesion between T3-L3 affect?

Answer 5

pelvic limbs only- paraparesis

Question 6

what will a lesion between L4-S1 affect?

Answer 6

pelvic limbs and tail

Question 7

what will a lesion caudal to the sacrum affect?

Answer 7

gait and pelvic limbs not affected! all nerves have come off that give rise to the names nerves of the pelvic limb already

Question 8

if only pelvic limbs are affected, what are the only 2 possible locations of a lesion?

Answer 8

1. T3-L3
2. L4-S1

Question 9

if all 4 limbs are affected (with normal mentation and cranial nerves) what are the 3 possible locations of a lesion?

Answer 9

1. C1-C5
2. C6-T2
3. diffuse neuromuscular (all LMN units affected in some way)

Question 10

are lesions of the spinal cord contralateral or ipsilateral?

Answer 10

ipsilateral (a lesion in the cervical spinal cord on the left will cause deficits on the left)

Question 11

what is observed when there is a lesion between C1-C5? (5)

Answer 11

1. UMN to all 4 limbs affected
2. LMN not affected
3. UMN weakness/ataxia
4. propriopceptive ataxia
5. normal to increased tone and little to no atrophy

Question 12

what is observed when there is a lesion between C6-T2? (2) the fun one!

Answer 12

1. LMN affected in thoracic limbs
2. UMN and proprioceptive ataxia in pelvic limbs

Question 13

describe thoracic limbs (3) and pelvic limbs (4) during a C6-T2 myelopathy

Answer 13

thoracic limbs:
1. reduced withdrawals (hyporeflexive)
2. hypotonia
3. decreased muscle mass

pelvic limbs:
1. normal withdrawals
2. myotatic reflexes: normal to increased
3. normal to increased tone
4. normal muscle mass

Question 14

what is observed with a lesion between T3-L3? (2)

Answer 14

1. normal thoracic limbs
2. UMN weakness with proprioceptive ataxia in pelvic limbs